vb.net搜索按鈕多個查詢

Question

我正在vb.net中創建一個程序，並想知道是否有一種方法來執行多個查詢與一個按鈕，而無需添加第二個按鈕。

像我有兩個文本框，一個是日期，另一個是名稱。我想要做的是，如果我點擊搜索，並且日期和名稱框都填滿了，我希望它根據該日期搜索名稱。但如果只填寫名字，我想在這個名字下搜索所有內容。

這就是我所擁有的。現在它只做一個搜索：

Private Sub cmdSearch_Click(sender As System.Object, e As System.EventArgs) Handles cmdSearch.Click 
     Dim conn As New MySqlConnection 
     Dim myCommand As New MySqlCommand 
     Dim myAdapter As New MySqlDataAdapter 
     Dim myData As New DataTable 
     Dim SQL As String 
      SQL = "SELECT CONCAT(u.lastname, ', ', u.firstname) AS Name " _ 
     & ", start.timestamp `Time In` " _ 
     & ", end.timestamp `Time Out` " _ 
     & ", timediff(end.timestamp, start.timestamp) Duration " _ 
    & "FROM user u " _ 
     & ", user_group ug " _ 
     & ", (" _ 
      & "select * " _ 
       & ", (" _ 
       & "select event_id " _ 
       & "from event L2 " _ 
       & "where L2.timestamp > L1.timestamp " _ 
        & "and L2.user_bannerid = ?bannerID " _ 
        & "and L1.user_bannerid = ?bannerID " _ 
       & "order by timestamp limit 1 " _ 
       & ") stop_id " _ 
      & "From event L1 " _ 
      & ") start " _ 
    & "join event end on end.event_id = start.stop_id " _ 
    & "where start.status = 'In' " _ 
     & "and end.status='Out' " _ 
     & "and u.user_bannerid = ?bannerID " _ 
     & "and start.user_bannerid = ?bannerID " _ 
     & "and ug.user_bannerid = ?bannerID " _ 
     & "and ug.group_id = ?GroupID " _ 
     & " and start.group_id = ?GroupID " _ 
    & "UNION " _ 
    & "SELECT null, null, null, CAST(sum(duration) as Time) " _ 
    & "FROM " _ 
    & "(" _ 
     & "SELECT CONCAT(u.lastname, ', ', u.firstname) AS Name " _ 
      & ", start.timestamp `Time In` " _ 
      & ", end.timestamp `Time Out` " _ 
      & ", timediff(end.timestamp, start.timestamp) duration " _ 
     & "from user u " _ 
      & ", user_group ug " _ 
      & ", (" _ 
       & "select * " _ 
       & ", (" _ 
       & "select event_id " _ 
       & "from event L2 " _ 
       & "where L2.timestamp > L1.timestamp " _ 
        & "and L2.user_bannerid = L1.user_bannerid " _ 
       & "order by timestamp " _ 
       & "limit 1 " _ 
       & ") stop_id " _ 
       & "from event L1 " _ 
      & ") start " _ 
     & "join event end on end.event_id = start.stop_id " _ 
     & "where start.status = 'In' " _ 
      & "and end.status = 'Out' " _ 
      & "and u.user_bannerid = ?bannerID " _ 
     & "and start.user_bannerid = ?bannerID " _ 
     & "and ug.user_bannerid = ?bannerID " _ 
     & "and ug.group_id = ?GroupID " _ 
     & " and start.group_id = ?GroupID " _ 
    & ") total " 
      conn.ConnectionString = myConnString 

      Try 
       conn.Open() 

       Try 
        myCommand.Connection = conn 
        myCommand.CommandText = SQL 
        myCommand.Parameters.Add("?bannerID", txtBannerID.Text) 
        myCommand.Parameters.Add("?GroupID", cboGroups.SelectedValue) 

        myAdapter.SelectCommand = myCommand 
        myAdapter.Fill(myData) 

        dgvStatus.DataSource = myData 
        dgvStatus.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.Fill 
       Catch myerror As MySqlException 
        MsgBox("There was an error reading from the database: " & myerror.Message) 
       End Try 
      Catch myerror As MySqlException 
       MessageBox.Show("Error connecting to the database: " & myerror.Message) 
      Finally 
       If conn.State <> ConnectionState.Closed Then conn.Close() 
      End Try 

     End Sub 

Answer 1

您可以通過點擊按鈕時檢查文本框來做到這一點。查詢是複雜的可能是相當困難的直接工作，但它歸結爲構建命令字符串，你想是這樣的：（路簡體）

查詢字符串建築：

​​

附加參數，如果它在where子句中

... Connection stuff here 

    myCommand.CommandText = SQL 
    If txtname.text.Trim <> "" Then 
     myCommand.Parameters.Add("?Name", txtName.Text.Trim) 
    End If